New Schiff base ligand H2L containing N2O4S donor atoms has been explored for its ability to provide complexes of selected 3d and 4f metal ions. Room temperature reaction of H2L with NiCl2·6H2O and Ln­(NO3)3·5H2O in the presence of Et3N in MeCN–MeOH (2:1) medium resulted in [Ni4Ln2(L)2(μ-Cl)2(μ3-OH)4(H2O)6]­Cl4·2H2O (where Ln = Dy3+ (1), Tb3+ (2), and Ho3+ (3) and H2L = 2-((2-(2-(2-hydroxy-3-methoxybenzylideneamino)­ethylthio)­ethylimino)­methyl)-6-methoxyphenol). Use of Ni­(SCN)2·4H2O during synthesis provided SCN– ions for bridging and terminal coordination in [Ni4Ln2(L)2(μ-NCS)2(μ3-OH)4(NCS)4(H2O)2]·xMeOH·yH2O (where Ln = Dy3+ (4), x = 2, y = 4; Tb3+ (5) and Ho3+ (6), x = 0, y = 14.1). All six complexes possess a hexanuclear defective tetracubane topology having exchangeable bridging groups. The study of direct current magnetic susceptibility measurements revealed that the Ni­(II) ions are engaged in ferromagnetic interaction with the DyIII, TbIII, and HoIII ions and have significant magnetic anisotropy in all six complexes. Alternating current susceptibility measurements confirmed that both of the two types of compounds qualify as zero-field single-molecule magnets (SMMs), and the effective barrier for the reversal of the magnetic moment was found to be in the range U eff = 23–31 K for 1–2 and 4–5, respectively. Detailed insight into the electronic structure and magnetic properties was calculated using DFT- and CASSCF-based analyses. The found isotropic exchange parameter (J) values are J Ni–Ni = −4.7 cm–1 for 1 and J Ni–Ni = +29.2 cm–1 for 4 and clearly indicate that the μ-NCS-bridge is a better candidate than μ-Cl for ferromagnetic exchange interactions. Out of the six complexes, only complex 5 displays TbIII centered emission peaks at 451 and 480 nm.

The versatility for a unique aggregation of heterometallic 3d–4f and 3d–3d′–4f ions by the new Schiff base ligand 2-{[(2-hydroxy-3-methoxybenzyl)­imino]­methyl}­phenol (H2L) providing O3N donors has been examined. A series of complexes having the general formula [Ln2Ni4(L)4(μ1,3-CH3CO2)2(μ3-OH)4(MeOH)2]·xCH3OH·yH2O [where Ln = DyIII, x = 4, y = 0 (1), Ln = TbIII, x = 0, y = 4 (2), and Ln = HoIII, x = 4, y = 0 (3)] were obtained from the sequential use of lanthanide­(III) nitrate salts and Ni­(CH3CO2)2·4H2O. The incorporation of two different 3d ions and one 4f ion in the same coordination aggregate was achieved through the isomorphic replacement of two NiII centers by MnIII ions as second group of cationic complexes, [Ln2Ni2Mn2(L)4(μ1,3-CH3CO2)2(μ3-OH)4(MeOH)2]­(NO3)2·2CH3OH [where Ln = DyIII (4), TbIII (5), and HoIII (6)]. Direct-current (dc) magnetic susceptibility studies hint to the possibility of ferromagnetic interactions occurring in the aggregates, whereas alternating-current susceptibility measurements find both the DyIII analogues, 1 and 4, to show out-of-phase components at zero applied dc field, characteristic of single-molecule-magnet (SMM) behavior. Micro-SQUID studies reveal open hysteresis loops for 1, corroborating its SMM character. Further detailed complete-active-space self-consistent-field and density functional theory calculations were also performed, supporting the experimental findings in complexes 1 and 4.

Octanuclear NiII5LnIII3 complexes obtained with ligand H2L show ferromagnetic interactions for Ni5Dy3 and Ni5Tb3 while antiferromagnetic interactions for Ni5Ho3.

A family of four isostructural [Ln2Ni2(L)2(μ3-OCH3)2(μ1,3-PhCO2)2(PhCO2)2(CH3OH)4]∙2CH3OH [where Ln = Gd (1), Tb (2), Dy (3) and Ho (4)] complexes has been synthesized using Schiff base ligand 2-[{(2-hydroxybenzyl)imino}methyl]-6-methoxyphenol (H2L). All the...